But all at once there came a sudden end to his practice.  Stacy’s pony suddenly leaped to one side, planting its front feet firmly on the ground and arching its back like an angry cat at bay.  Stacy did a beautiful curve in the air, landing on his shoulders on the hard ground.  He had a narrow escape from breaking his neck.

The Rangers howled.  They were still bowling when Stacy, getting his breath back, sat up, bunching his shoulders to get the kink out of them, and rubbing himself gingerly.  The pony stood looking at its young master sheepishly.

“What’s the trouble, Stacy?” cried Tad riding back.

“I—–­I fell off.”

“I know you did.  There couldn’t be any mistake about that, but what caused him to throw you?”

“I—–­I don’t know.”

“That pony was frightened at something.  What was it?” demanded the captain of Cad Morgan.

“I’m blest if I know, Captain.  There wasn’t anything that I saw.”

“Take a scout around through the brush, you and Polly.  There may be some one taking a parallel trail.”

“Yes, there may be some German raiders hiding out there in the bush, laying for us.  We ought to have some bombs.  They would clean those fellows out in short order,” declared Stacy.

The two men trotted from the line and disappeared among the trees, while the fat boy got back in his saddle, somewhat more sad, but no wiser than before.  But he was thinking a great deal.

“He must have got scared at some of my imitations,” decided the lad.  “I don’t blame him.”

“But which one was it?  I’ll see if I can do them again.”

Letting his horse drop back a few rods behind the others, Chunky went over his list of accomplishments in the imitation line, trying each one cautiously, keeping a watchful eye on the ears of the pony.

All at once the eyes of the fat boy lighted up.  Something struck him as funny.  He laughed aloud.

“Chunky’s got them again,” chuckled Ned Rector.

Stacy waited until all hands were looking ahead when he tried the imitation that he believed had caused his mount to halt.  His success was instantaneous.  The pony leaped clear of the ground, coming down with a jolt that made the boy’s head ache.

“What’s the matter with that horse?” called Captain McKay.

“Guess he’s feeling his oats,” flung back Chunky.  The boy hugged himself delightedly.  What he had done was to give a trilling tongue movement accompanied by a hiss.  It was a perfect imitation of the trilling hiss of the rattlesnake.  When Stacy had first given the imitation he did not realize what he was doing.  He had fooled his pony.  The Pony Rider Boy was delighted.  He tried it again with equal success, though this time he was thrown forward on the neck of his mount.  This jolt nearly broke Stacy Brown in two.

“That was the blow that near killed papa,” grinned the lad.  “I never knew I could do that.  I reckon.  I’ll be having some fun with this outfit.  Yes, I’ll try it on right now.”